


Common Knowledge

by willgrahamchops



Category: Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: Autoerotic Asphyxiation, Breathplay, Case Fic, M/M
Language: English
Status: Completed
Published: 2013-03-20
Updated: 2013-03-20
Packaged: 2017-12-05 21:07:17
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,048
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/727937
Author URL: https://archiveofourown.org/users/willgrahamchops/pseuds/willgrahamchops
Summary: <blockquote class="userstuff">
              <p>
  <i>Leave work early. I need you to strangle me. -SH</i>
</p>
            </blockquote>





	Common Knowledge

**Author's Note:**

> Title from Bright Eyes. 
> 
> _So many times he's tried to play it straight  
>  Worked and worked until his body ached  
> But a brand new life can lose its lustre  
> Troubles tend to find each other  
> Call it luck or you can call it fate_

_Leave work early. I need you to strangle me. -SH_

John is on his lunch break. He almost doesn't check his phone when it vibrates, and when he does he regrets it.

It's always something like this. He takes a deep breath and pinches the bridge of his nose.

“Something wrong?” Sarah asks through a mouthful of quiche, somehow still managing to sound concerned.

“No,” John sighs. “It's – Sherlock is having a personal crisis.” He watches as Sarah's face falls visibly. He feels sorry for her. She has to put up with this just as much as John does. He's going to say something more when his phone vibrates again, making them both jump.

_If you don't come home I'm going to do it myself. -SH_

Sarah frowns and sets down her fork. “Can I help?”

“Um.” John is busy texting back. “Maybe. Hang on a moment.” But before he even finishes his text, another one appears in his inbox.

_If you're going to stop me you'll have to leave work anyway, so you might as well call a cab. -SH_

He erases what he was typing and sends instead:

_Can't this wait? -JW_

“Could you cover me for the rest of the day?” He asks, still looking at his phone.

_Police have wasted enough time already. -SH_

Sarah is saying something but John isn't listening; he's imagining arriving at 221B to find that his flatmate has choked himself to death. “Thank you,” he says absently. “You're amazing. I'll see you tomorrow.” And then he's in a cab, and he's trying not to imagine Sherlock hanging from the rafters.

The first thing he hears when he arrives at Baker Street is Sherlock shouting down the stairs, which is a good sign. “Are you wearing your Huntsman belt?”

Sherlock's not on the first floor, which means he must be in John's room. In John's–

“What are you doing in my closet?” He asks accusingly.

Sherlock looks up from his place on the floor, John's clothes strewn all around him, and says, “Belt. Off.” He makes a grabbing motion with his hand. John apparently fails to remove his belt as quickly as Sherlock would like, because Sherlock suddenly springs to his feet and removes it himself while John sputters.

“You had better have a _damn_ good explanation–”

“Yes. Four and a half centimeters, calf leather, Huntsman. A good belt, _and_ it matches the victim's in every aspect except color.” Sherlock grimaces. “Really, John, black with tan Oxfords?”

John chooses to ignore the jab in favor of, “What _vicim_? You keep talking about a–”

“Yes, of course.” Sherlock, who has finally succeeded in removing the belt, snaps it taut between his hands, assessing the weight of the leather. “Edward McGuffey, thirty-six, stock broker's clerk. Official cause of death is autoerotic asphyxiation.” He looks pointedly at John.

This is for real, then, John realizes, not just some neurotic fancy. Not something he can easily dissuade. He sighs. Sherlock watches him intently. “But it wasn't self-inflicted,” he says.

Sherlock shakes his head. “It wasn't asphyxiation at all. The corpse showed preliminary signs of hypoxia but almost no cyanosis, very little discoloration.”

John frowns. “So that means... he was dead before he was hanged?”

A grin spreads across Sherlock's face, almost predatory. John no longer bothers to be surprised by the things that excite his flatmate. “Good, John,” he says. “McGuffey appears to have stumbled upon a rather large conspiracy to play the market. Several prominent companies are involved. He's made some enemies.”

“So somebody murders this man – what are you thinking?”

“Poison,” says Sherlock. “And the killer was personally involved, not a trained assassin.”

“Okay,” John says, rolling his shoulders. He's tense, watching Sherlock handle the belt almost fondly, and he's not sure why. “Explain.”

“Obvious. He poisoned McGuffey and then faked his hanging. What's the point? Why not just hang him in the first place? Think, John. Do you see it?”

And suddenly, John does. “The hypoxia,” he breathes. “Of course. The killer tries to asphyxiate McGuffey, loses his nerve–”

“And stuffs him full of Prolixin from the medicine cabinet. Clever, as Prolixin is nearly untraceable,” Sherlock finishes.

“ _Prolixin?_ ” John asks. “A schizophrenic stockbroker's clerk?”

Sherlock smiles. “So it seems.”

And they lock eyes. Slowly, deliberately, Sherlock loops the belt and threads it through the buckle, pulling the slack until the opening is slightly bigger than his head.

John opens his mouth to protest but Sherlock beats him to it, saying, “I need to know how long he was choked before the killer got nervous.”

John says, “ _Why?_ ”

Then Sherlock springs into action, crossing the room to John's bed in two long strides and kneeling on the duvet. His robe falls open to reveal loose cotton trousers and a grey tee. “Keep up,” Sherlock says, speaking quickly now, giddy with anticipation. “McGuffey's medical records showed no signs of psychosis, so the Prolixin was either recreational–” Sherlock grimaces, and John can't help but mirror his expression. Recreational anti-psychotics? “–Or someone brought it to the scene. If we find out how long he was strangled, we'll know whether the killer brought the pills as a back up or summoned an accomplice.”

“And you're going to find out–”

“ _You_ are going to find out,” Sherlock corrects, “by choking me until the preliminary stages of hypoxia.”

John glances around the room, subconsciously looking for an escape. He knows _I don't want to do it_ is not an acceptable excuse. “This information isn't already available?” He asks instead.

Sherlock waves a hand dismissively. “Too many variables. The weight of the belt was unusual, and the force was applied perpendicular to the victim's neck, rather than the typical parallel hanging. These results will be much more accurate.”

And that's that. John's stumped.

Sherlock raises one delicate eyebrow. “Would you like to use my stopwatch?”

And John doesn't; he really, _really_ doesn't want to be responsible if something goes wrong, isn't comfortable with Sherlock trusting him so thoroughly. He's a doctor. He _fixes_ injuries.

Sherlock reads this on his face, typical. He rolls his eyes. “You have bad days; you said it yourself.”

“This isn't one of them!” John insists. “Christ, Sherlock, I don't want to–”

“Don't want arrest one or possibly two murderers? Don't want to deliver _justice_?” He sneers as the word passes his lips.

John's mouth snaps shut.

Sherlock says, “I'll do it myself if you won't, and it won't be nearly as safe. And then it will be your fault anyway, if I hurt myself.”

John says, “Why don't you do it to me?”

There's a pause, an exhalation.

“What?”

“Choke me,” John says. “You'll collect better data anyway. You know the stages of asphyxiation as well as I do.”

Sherlock frowns as if the the thought hasn't previously occurred to him, which is strange because using John as a lab rat always seems to occur to him. Slowly, he says, “You trust me to–?”

“I've trusted you to drug me, get me out of jail, break my little finger, and cut my hair. Yes, I trust you to choke me.” John doesn't mention that the haircut was awful and the jail time was two days longer than promised, because that doesn't really have any bearing on his trust, even though it should.

“You're absolutely sure?” Sherlock asks.

John sets his jaw and nods.

“Fine,” he says, climbing off the bed. “Get up. The victim was pinned to the couch, but ours is too low so this will have to do. Kneel on the edge, that's right.”

John is determined to do this properly, if only to prevent Sherlock from repeating the experiment. He kneels obediently.

“Undo your top three buttons.” He's cold, clinical, and it soothes John's nerves. “We're aiming for diffuse cerebral hypoxia. Any signs of ischemia and we've gone too far, so I need you to tell me immediately.”

“I'll need a signal,” John prompts, trying to keep his voice steady. 

“Of course. You'll rest your hand on my knee. One squeeze for giddiness, lightheadedness – that's good; we want that. Two squeezes for darkening vision. Tap out–” Sherlock smacks his hand against the duvet to demonstrate. “–For any numbness or tingling, especially in the face. You must let me know immediately if that happens.”

John nods.

“Good,” says Sherlock. “Shall we begin?”

He searches inside for some protest, but nothing occurs to him. John shrugs, already rather resigned to his fate. “Might as well.”

With a curt nod Sherlock, still standing and just slightly above eye level, fits the belt around John's neck. John swallows as the cold leather presses into his jugular, not tight yet. “Can you, uh – can you talk to me while you do it?”

The belt loosens just a bit. Sherlock pauses, and then says, “Of course.” Sherlock knows what he means.

Then it's snug around his neck once more. Sherlock rotates the belt so that the buckle and the lead are in the back. “The victim was facing away from his killer, but I need to monitor your reactions, so I'm pulling backwards.” John nods minutely. “Hold still,” Sherlock says. John rolls his eyes. “Try to even your breathing. Now take a breath, no deeper than usual.”

John does, and before he quite finishes, Sherlock snaps his wrist and the belt tightens around his throat, cutting the breath short. John chokes.

Sherlock smiles lazily and takes hold of John's wrist, gently guiding it to his knee. He doesn't let go but instead presses his thumb to John's pulse point, no doubt mentally keeping track. “Good,” he says. “Lovely.”

John doesn't feel lovely. His face is already heating up. It's been less than ten seconds and it feels like there's no more oxygen in his lungs.

“Don't hold it,” Sherlock says. “Keep trying to breathe, even if you can't. The victim would be panicking. Don't struggle; we don't want you bruising yet, but try as hard as you can to breathe.”

John does. It hurts, trying to suck in air through a crushed windpipe, but he tries anyway, and – there, a tiny breath. Relief washes over him, even though it's short lived.

“The killer's hands are shaking. He's trying to maintain his grip, but every once in awhile he _slips_ ,” and on that word Sherlock allows him another small gulp of air. John's eyelids flutter. 

He suddenly remembers the signals and hastens to squeeze Sherlock's knee, once for giddiness.

“Good,” Sherlock says. His eyes are narrowed, watching John's face intently, and a smile pulls at his lips. John is not surprised that he's enjoying this. “Keep breathing. It's been thirty-three seconds.”

Thirty-three. It seems so much longer than that, time stretching endlessly before him. He wonders vaguely how long this will last. With his stature and fitness, how long would it take for him to pass out? A minute is the usual maximum, but Sherlock's letting him breathe, just a bit, just sometimes.

“Beautiful,” Sherlock whispers. John doesn't think he's even aware he's doing it.

John grunts. Sherlock raises an eyebrow. “Vision?” He asks, and John squeezes his knee twice for darkening vision. Sherlock does something John can't see with his free hand. It'll be over soon, John assumes, since he's on the verge of passing out.

Except, Sherlock gives him another breath, deeper than the previous few but still not quite enough. It hurts; it pulls him back from the brink of unconsciousness and rips through him, making his head throb. He makes some involuntary noise that sets Sherlock smiling again. John might smile too at his characteristic enthusiasm, were he able to smile. Two squeezes. Darker.

Sherlock lets him breathe. “Lovely, John,” he smiles. “You're doing so well.” 

John vaguely registers Sherlock's hand moving, departing from his pulse point and sliding up his arm, dipping between his collarbones to play above his carotids. 

Two squeezes. The darkness comes more frequently now. Surely he's reached preliminary hypoxia by now, but Sherlock tightens the belt once again. John involuntarily mouths Sherlock's name.

John doesn't know how Sherlock is monitoring his condition with his face pressed into John's hair. “Gorgeous,” Sherlock whispers, breath hot in John's ear. “So pretty when you're hurting. Do you think you can last another thirty seconds?”

John doesn't have much of a choice. He can still tap out, but Sherlock said numbness and there is no numbness yet. He wonders how long this has been going on. He reaches a point where he stops feeling pain and starts floating, warm and fuzzy around the edges. His brains slows down. Everywhere Sherlock touches him is a spark in the darkness.

“Ten,” says Sherlock. He croons praise in John's ear. John wonders what he did to deserve this. “One more breath,” says Sherlock. “You can make it on that.”

It's fleeting, and it hurts. The choking in much more pleasant than the breathing.

“Five,” says Sherlock, almost a growl. He twists the belt around his wrist to pull it as tight as possible. Something in John's head is going to burst; he's sure of it, but he's not numb and he's not going to tap out.

For a long second their eyes lock, John's vision dark and blurry and Sherlock's eyes razor sharp.

Sherlock releases him.

The first thing John does is double over and cough until his chest screams for him to stop and his shoulder flares with pain. The rush of his first real breath is completely overwhelming, like jumping into freezing water. His second hurts just as much.

Sherlock's hands are on him, and he realizes that he almost rolled off the bed only once Sherlock has shifted him safely away from the edge.

He blinks furiously, trying to steady his spinning vision.

There's a hand on his waist. “...More than I expected,” Sherlock is saying. John shakes his head. His ears are ringing.

The first thing he says is simply, “What?” Not very eloquent. Sherlock is undoubtedly disappointed.

“Two minutes, but hypoxia set in at one and fifteen seconds. I took pressure off your carotid arteries after that. Thumb under the belt.” He wiggles his fingers. 

“Nng,” says John. He must have been impossibly far gone not to notice that.

“Because you liked it,” Sherlock says. He hadn't asked why Sherlock kept going, but the answer makes things no clearer.

John mumbles something that means _what_ , at its core. He curses his sluggish brain.

Sherlock doesn't answer. Instead he unbuttons John's fly, and things suddenly fall into place.

“No,” John groans. It's a weak protest, one of humiliation rather than discomfort.

“We're not going to ruin the experiment,” Sherlock says, as if that's what John is nervous about. “The experiment ended a minute and fifteen seconds in. Two killers.” He will ask how Sherlock reasoned that out later. “And now I would like to definitively rule out the erotic aspect.”

He's going to argue, _how will tugging me off help you do that_ , but the first brush of Sherlock's slender fingers against his cock kills all protest. He pulls in a ragged breath.

“Breathe normally,” Sherlock says. “Keep your head down. Relax your muscles.”

John does. This is surprisingly easy when Sherlock draws it up as an experiment, and he is _painfully_ hard, though he didn't realize it until the belt came off.

“I must admit, I understood the appeal of autoerotic asphyxiation on the chemical level, but the emotional reasoning escaped me at first. I didn't expect you to become so aroused.”

John opens his mouth to defend himself, but Sherlock shushes him with a finger to his lips.

“I didn't expect to be so affected myself,” Sherlock concedes. It's only then that John glances downward to find that Sherlock is indeed hard in his trousers. John is far from surprised; in fact, he should have seen this coming. “Don't get used to my disrupting data collection for you, John.”

“Sod off,” John gasps.

“Hush,” says Sherlock. “Or the tissue in your throat won't bruise properly.”

John is a doctor, and he knows that's utter bullshit – Sherlock just doesn't want him to talk while he does this. That's alright for now, though. He keeps his mouth shut.

Sherlock abruptly takes John's pulse. “Close, aren't you?” He says, voice husky.

“You needed my pulse to tell you that?”

Sherlock ignores him in favor dragging his fingers down John's throat, tracing the marks left by the belt. He lightly digs a nail into the deepest part of the indentation. “On the right,” he says, mostly to himself. “Clearer, so the killer pulled slightly to the left.” 

John bucks involuntarily into Sherlock's hand.

Sherlock keeps a straight face. “Go ahead, then,” he says.

John does, all over Sherlock's hand and his own shirttails, quick and intense and immensely satisfying. Sherlock strokes him through it until his touch is painful, and then keeps going until John tries to twist out of his grip.

He examines the mess on his hand while John watches through lidded eyes. It's as though he's never seen come before.

“Don't play with it,” John says.

Sherlock wrinkles his nose but says nothing, instead wiping his hand on John's sheets.

John stretches lazily. “Want me to take care of yours too?”

Sherlock shakes his head.

“Suit yourself.”

“I'll just need a moment,” Sherlock says, composure perfectly intact once more. “Then I need pictures of the bruising. You were strangled longer than the victim, but you didn't struggle. The imprint of the belt should–”

John waves a hand, shushing him. “I'm going to take a nap,” he says. “You can either take pictures while I sleep or after I'm done, but God help me Sherlock, if you wake me up, I will never answer your texts ever again.”

“An empty threat,” Sherlock says.

John points to the door. “Sleeping,” he says. “Now.”

Sherlock makes a show of his indignity, stomping out of the room as if letting John sleep is an enormous hardship. John sighs contentedly and rolls onto his side.

When he wakes up and sidles downstairs, he finds Sherlock working on his laptop – _John's_ laptop – poring over the photos.

“Are those–?”

“Yes, obviously. The victim is on the right; you're on the left.”

He doesn't ask how Sherlock managed to photograph the inside of his mouth without waking him up.

**Author's Note:**

> Thanks to everybody who explored this prompt with me on Omegle!


End file.
